We all knew Google was going to announce its new Google Music service today because it leaked the news last night. The service has now gone live and is available for US users only to request and invitation.

Here’s what Google has to say about how Music will work.

Music Manager is a program for Windows and Mac that will add users music. You can import iTunes ratings, music and playlists into it. The interface looks minimal and relatively attractive.

When you create a playlist it will be instantly available across the platforms. All of your Google music is available in the cloud to all of your devices. The new music interface for the Honeycomb platform takes advantage of these syncing options.

Instant Mix is a feature that instantly creates a playlist based on your music selections. This is similar to Apple’s Genius feature in iTunes.

Recently played music is automatically cached by tablets and phones for offline play. This is in addition to a feature that allows you to manually download music for offline play.

When you get a new phone, you just sign in to your Google account and all of your music is available immediately.

You can add up to 20,000 songs to your library and while it’s in beta it’s free. All Google I/O attendees got a beta invite.

Any Android device running version 2.2 or above can grab the new Music service on their device today.

Listen anywhere, even offline.

You can get to your personal music collection at home or on the go. Listen from the web or any enabled device with the Music app available from Android Market. Not online? No problem. The songs you’ve recently played will automatically be available offline. You can also select the specific albums, artists and playlists you want to have available when you’re not connected.

Stay in sync, without the hassle.

Spend more time listening to your music and less time managing it. Once your music is online, it’s always available. Playlists are automatically kept in sync, and you don’t have to worry about cables, file transfers, or running out of storage space.

Your collection, now in one place.

Upload your personal music collection to a single library, even if it’s scattered across multiple computers. You can upload music files from any folder or add your iTunes library and all of your playlists. And when you add new music to your computer, it can be automatically added to your music collection online.

Mix it up.

Create your own custom playlists with just a few clicks. Or use Instant Mix to automatically build new playlists of songs from your collection that go great together. All the playlists you create and all the changes you make to them are automatically available everywhere your music is.